If A needs 5 hrs to paint a house n B needs 3hrs to do the same, how much time will they need if 2 of them paints the house tog?
2007-01-02 02:44:25 · 8 answers · asked by kokleongl 1 in Science & Mathematics ➔ Mathematics
A needs 5 hrs to paint a house
In one hour he does 1/5 th painting job
B needs 3 hrs to paint a house
In one hour he does 1/3 rd painting job
In one hour both A & B do (1/5)+(1/3) of the painting job!
=8/15 of the painting job
Therefore paintin job is completed by 1/(8/15) hrs = 15/8 hrs = =1.875 hrs
= 1 hr 52 min 30 sec
2007-01-02 02:47:15 · answer #1 · answered by Som™ 6 · 1⤊ 1⤋
A = 1/5 in one hour
B = 1/3 in one hour
together = 1/5 + 1/3 = 8/15 in one hour
8/15 = 1 hour
15/15 = x hours
8 = 60 minutes
7 = (15-8) = x minutes
7 x 60 divide by 8 = 52.5 minutes
1 hour + 52.5 min = 1 hr 52.5 min to paint house
2007-01-02 12:27:50 · answer #2 · answered by David C 2 · 0⤊ 1⤋
...
A can paint 1/5 of the house in an hour.
B can paint 1/3 of the house in an hour.
With both of them working at the same time, they can paint
1/3 + 1/5 = 8/15 of the house in an hour.
It will take them 1/(8/15) = 15/8 of an hour to paint the house.
That equals 112.5 minutes or 1 hour and 52.5 minutes.
...
2007-01-02 10:50:22 · answer #3 · answered by Jon 3 · 1⤊ 1⤋
In 1 hour ---
A does 1/5 and B does 1/3
A + B together in 1 hour = 1/5 + 1/3 = 8/15
Total hours needed = 1 (whole work=1) /(8/15)
= 15/8 hours
= 1.875 hours
2007-01-02 10:55:30 · answer #4 · answered by Sheen 4 · 0⤊ 1⤋
A does 1/300 of the job in a minute
B does 1/180 of the job in a minute
A+B do - 1/300 + 1/180 = 8/900 of the job
The complete job will take 900/8 minutes or 112.5 minutes.
2007-01-02 10:53:20 · answer #5 · answered by Anonymous · 0⤊ 1⤋
Ya exactly 15/8 hrs to finish de work
k
2007-01-02 12:14:36 · answer #6 · answered by Sathish 1 · 0⤊ 0⤋
It is 2 hours
2007-01-02 10:46:29 · answer #7 · answered by Suhas 2 · 0⤊ 2⤋
two and a half hours!
2007-01-02 10:47:11 · answer #8 · answered by francisterence 3 · 0⤊ 2⤋